linux/drivers/usb/host/ehci-sysfs.c
Kirill Smelkov cc62a7eb63 USB: EHCI: Allow users to override 80% max periodic bandwidth
There are cases, when 80% max isochronous bandwidth is too limiting.

For example I have two USB video capture cards which stream uncompressed
video, and to stream full NTSC + PAL videos we'd need

    NTSC 640x480 YUV422 @30fps      ~17.6 MB/s
    PAL  720x576 YUV422 @25fps      ~19.7 MB/s

isoc bandwidth.

Now, due to limited alt settings in capture devices NTSC one ends up
streaming with max_pkt_size=2688  and  PAL with max_pkt_size=2892, both
with interval=1. In terms of microframe time allocation this gives

    NTSC    ~53us
    PAL     ~57us

and together

    ~110us  >  100us == 80% of 125us uframe time.

So those two devices can't work together simultaneously because the'd
over allocate isochronous bandwidth.

80% seemed a bit arbitrary to me, and I've tried to raise it to 90% and
both devices started to work together, so I though sometimes it would be
a good idea for users to override hardcoded default of max 80% isoc
bandwidth.

After all, isn't it a user who should decide how to load the bus? If I
can live with 10% or even 5% bulk bandwidth that should be ok. I'm a USB
newcomer, but that 80% set in stone by USB 2.0 specification seems to be
chosen pretty arbitrary to me, just to serve as a reasonable default.

NOTE 1
~~~~~~

for two streams with max_pkt_size=3072 (worst case) both time
allocation would be 60us+60us=120us which is 96% periodic bandwidth
leaving 4% for bulk and control.  Alan Stern suggested that bulk then
would be problematic (less than 300*8 bittimes left per microframe), but
I think that is still enough for control traffic.

NOTE 2
~~~~~~

Sarah Sharp expressed concern that maxing out periodic bandwidth
could lead to vendor-specific hardware bugs on host controllers, because

> It's entirely possible that you'll run into
> vendor-specific bugs if you try to pack the schedule with isochronous
> transfers.  I don't think any hardware designer would seriously test or
> validate their hardware with a schedule that is basically a violation of
> the USB bus spec (more than 80% for periodic transfers).

So far I've only tested this patch on my HP Mini 5103 with N10 chipset

    kirr@mini:~$ lspci
    00:00.0 Host bridge: Intel Corporation N10 Family DMI Bridge
    00:02.0 VGA compatible controller: Intel Corporation N10 Family Integrated Graphics Controller
    00:02.1 Display controller: Intel Corporation N10 Family Integrated Graphics Controller
    00:1b.0 Audio device: Intel Corporation N10/ICH 7 Family High Definition Audio Controller (rev 02)
    00:1c.0 PCI bridge: Intel Corporation N10/ICH 7 Family PCI Express Port 1 (rev 02)
    00:1c.3 PCI bridge: Intel Corporation N10/ICH 7 Family PCI Express Port 4 (rev 02)
    00:1d.0 USB Controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #1 (rev 02)
    00:1d.1 USB Controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #2 (rev 02)
    00:1d.2 USB Controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #3 (rev 02)
    00:1d.3 USB Controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #4 (rev 02)
    00:1d.7 USB Controller: Intel Corporation N10/ICH 7 Family USB2 EHCI Controller (rev 02)
    00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev e2)
    00:1f.0 ISA bridge: Intel Corporation NM10 Family LPC Controller (rev 02)
    00:1f.2 SATA controller: Intel Corporation N10/ICH7 Family SATA AHCI Controller (rev 02)
    01:00.0 Network controller: Broadcom Corporation BCM4313 802.11b/g/n Wireless LAN Controller (rev 01)
    02:00.0 Ethernet controller: Marvell Technology Group Ltd. 88E8059 PCI-E Gigabit Ethernet Controller (rev 11)

and the system works stable with 110us/uframe (~88%) isoc bandwith allocated for
above-mentioned isochronous transfers.

NOTE 3
~~~~~~

This feature is off by default. I mean max periodic bandwidth is set to
100us/uframe by default exactly as it was before the patch. So only those of us
who need the extreme settings are taking the risk - normal users who do not
alter uframe_periodic_max sysfs attribute should not see any change at all.

NOTE 4
~~~~~~

I've tried to update documentation in Documentation/ABI/ thoroughly, but
only "TBD" was put into Documentation/usb/ehci.txt -- the text there seems
to be outdated and much needing refreshing, before it could be amended.

Cc: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Kirill Smelkov <kirr@mns.spb.ru>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2011-07-08 14:51:33 -07:00

190 lines
5.2 KiB
C

/*
* Copyright (C) 2007 by Alan Stern
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/* this file is part of ehci-hcd.c */
/* Display the ports dedicated to the companion controller */
static ssize_t show_companion(struct device *dev,
struct device_attribute *attr,
char *buf)
{
struct ehci_hcd *ehci;
int nports, index, n;
int count = PAGE_SIZE;
char *ptr = buf;
ehci = hcd_to_ehci(bus_to_hcd(dev_get_drvdata(dev)));
nports = HCS_N_PORTS(ehci->hcs_params);
for (index = 0; index < nports; ++index) {
if (test_bit(index, &ehci->companion_ports)) {
n = scnprintf(ptr, count, "%d\n", index + 1);
ptr += n;
count -= n;
}
}
return ptr - buf;
}
/*
* Dedicate or undedicate a port to the companion controller.
* Syntax is "[-]portnum", where a leading '-' sign means
* return control of the port to the EHCI controller.
*/
static ssize_t store_companion(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
struct ehci_hcd *ehci;
int portnum, new_owner;
ehci = hcd_to_ehci(bus_to_hcd(dev_get_drvdata(dev)));
new_owner = PORT_OWNER; /* Owned by companion */
if (sscanf(buf, "%d", &portnum) != 1)
return -EINVAL;
if (portnum < 0) {
portnum = - portnum;
new_owner = 0; /* Owned by EHCI */
}
if (portnum <= 0 || portnum > HCS_N_PORTS(ehci->hcs_params))
return -ENOENT;
portnum--;
if (new_owner)
set_bit(portnum, &ehci->companion_ports);
else
clear_bit(portnum, &ehci->companion_ports);
set_owner(ehci, portnum, new_owner);
return count;
}
static DEVICE_ATTR(companion, 0644, show_companion, store_companion);
/*
* Display / Set uframe_periodic_max
*/
static ssize_t show_uframe_periodic_max(struct device *dev,
struct device_attribute *attr,
char *buf)
{
struct ehci_hcd *ehci;
int n;
ehci = hcd_to_ehci(bus_to_hcd(dev_get_drvdata(dev)));
n = scnprintf(buf, PAGE_SIZE, "%d\n", ehci->uframe_periodic_max);
return n;
}
static ssize_t store_uframe_periodic_max(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
struct ehci_hcd *ehci;
unsigned uframe_periodic_max;
unsigned frame, uframe;
unsigned short allocated_max;
unsigned long flags;
ssize_t ret;
ehci = hcd_to_ehci(bus_to_hcd(dev_get_drvdata(dev)));
if (kstrtouint(buf, 0, &uframe_periodic_max) < 0)
return -EINVAL;
if (uframe_periodic_max < 100 || uframe_periodic_max >= 125) {
ehci_info(ehci, "rejecting invalid request for "
"uframe_periodic_max=%u\n", uframe_periodic_max);
return -EINVAL;
}
ret = -EINVAL;
/*
* lock, so that our checking does not race with possible periodic
* bandwidth allocation through submitting new urbs.
*/
spin_lock_irqsave (&ehci->lock, flags);
/*
* for request to decrease max periodic bandwidth, we have to check
* every microframe in the schedule to see whether the decrease is
* possible.
*/
if (uframe_periodic_max < ehci->uframe_periodic_max) {
allocated_max = 0;
for (frame = 0; frame < ehci->periodic_size; ++frame)
for (uframe = 0; uframe < 7; ++uframe)
allocated_max = max(allocated_max,
periodic_usecs (ehci, frame, uframe));
if (allocated_max > uframe_periodic_max) {
ehci_info(ehci,
"cannot decrease uframe_periodic_max becase "
"periodic bandwidth is already allocated "
"(%u > %u)\n",
allocated_max, uframe_periodic_max);
goto out_unlock;
}
}
/* increasing is always ok */
ehci_info(ehci, "setting max periodic bandwidth to %u%% "
"(== %u usec/uframe)\n",
100*uframe_periodic_max/125, uframe_periodic_max);
if (uframe_periodic_max != 100)
ehci_warn(ehci, "max periodic bandwidth set is non-standard\n");
ehci->uframe_periodic_max = uframe_periodic_max;
ret = count;
out_unlock:
spin_unlock_irqrestore (&ehci->lock, flags);
return ret;
}
static DEVICE_ATTR(uframe_periodic_max, 0644, show_uframe_periodic_max, store_uframe_periodic_max);
static inline int create_sysfs_files(struct ehci_hcd *ehci)
{
struct device *controller = ehci_to_hcd(ehci)->self.controller;
int i = 0;
/* with integrated TT there is no companion! */
if (!ehci_is_TDI(ehci))
i = device_create_file(controller, &dev_attr_companion);
if (i)
goto out;
i = device_create_file(controller, &dev_attr_uframe_periodic_max);
out:
return i;
}
static inline void remove_sysfs_files(struct ehci_hcd *ehci)
{
struct device *controller = ehci_to_hcd(ehci)->self.controller;
/* with integrated TT there is no companion! */
if (!ehci_is_TDI(ehci))
device_remove_file(controller, &dev_attr_companion);
device_remove_file(controller, &dev_attr_uframe_periodic_max);
}